Compositions containing maleic anhydride-polypropylene graft copolymers, and a fatty acid polyamide or an amine aldehyde resin



Uited States Patent ABSTRACT OF THE DISCLOSURE Compositions aredisclosed comprising a maleic anhydride-modified propylene polymercontaining as a cross- 3,375,300 Patented Mar. 26, 1968 can be monomericor resinous. Examples of usable monomeric compounds fitting thisdescription are dicyclopentadiene dioxide, vinylcyclohexene dioxide,butadiene dioxide, 1,5-pentadiene dioxide, divinyltoluene dioxide andthe like. Examples of usable resinous compounds include such resins asthe reaction products of polyhydric phenols with polyfunctional epoxidecompounds in such proportions as to have terminal epoxy groups andepoxidized polydiolefins, such as butadiene, methyl butadiene,dimethylbutadiene, and the like. A large number of usable phenolepoxidecompounds of the type described are disclosed in Greenlee US. Patents2,585,115 and 2,589,245. A typical resin prepared by reactingepichlorohydrin with 2,2-bis (p-hydroxyphenyl) propane has thetheoretical structural formula linking agent a composition containing aplurality of epoxide groups, a polyamide resin or etherified aminealdehyde resin. These are useful as primers for adhering an unmodifiedpropylene polymer to wood or metal. The coated compositions thus exhibitimproved resistance to a salt spray atmosphere.

The present invention relates to a new composition of matter especiallyuseful as a primer for coating metal. More particularly, the compositionof the invention comprises a maleic anhydride-modified propylene polymerand a minor amount of a cross-linking agent therefor.

According to a prior unpublished proposal, it has been found that maleicanhydride-modified propylene polymers, i.e., solid polymers ofpropylene, which have been chemically combined with from about 0.05 toabout 5% by weight of maleic anhydride, are excellent primers for thecoating of metal. An outstanding characteristic of such primers is theiradhesion to metal. However, in ionic environments such as are frequentlyencountered under use conditions, metal coated by the use of suchprimers is sensitive, even when topcoated, to underfilm corrosioncreepage if a flaw is present in the coating. Corrosion creepage ismanifested by rusting of the metal substrate and loss of adhesionbetween the metal and the coating. This defect is particularlynoticeable when the primer coating is relatively thick, e.g. about 0.1to 1 mil. Thus the problem can be alleviated somewhat by using thinnercoatings. However, such thinner coatings are marginally combined withthe maleic anhydride-modified propylene polymer, are capable ofcross-linking the polymer by reaction with its anhydride or carboxylicacid functional group, and thereby reduce considerably thesusceptibility to underfilm rust creepage when used as a metal primer.The additives useful for this purpose are selected from the classconsisting of compounds containing a plurality of epoxide functionalgroups, etherified amine-aldehyde resins, and polyamide resins. One ormore of these additives are simply combined in small amount with amaleic anhydride-modified propylene polymer and then the composition isapplied by conventional techniques as a metal primer, and subsequentlyt-opcoated with any desired coating composition, e.g. crystalline oramorphous polypropylene.

The compounds containing a plurality of epoxide functional groups usefulin the compositions of this invention where n is 0 or an integer up to10, usually 2 or 3. Several such resins are commercially availableproducts. The epoxidized polydiolefins can be prepared by reacting apolymer of a conjugated diene with a lower aliphatic peracid in theratio of about one mole of the peracid for each epoxide functional groupsought to be introduced into the polymer molecule. The preparation ofepoxidized polydiolefins is more fully described in Greenspan et al.,US. Patents 3,010,976 and 2,826,556, inter alia.

The polyamide resins which are useful as cross-linking additives in thecompositions of this invention are relatively low molecular weightpolymers of the general formula where R and R are saturated orunsaturated aliphatic radicals and n is 0 or an integer from about 1 to10. They are prepared by the condensation of a dibasic fatty acid with aslight excess of an alkylene diamine. These resins have molecularweights generally in the range of 1,000 to 10,000 and softening pointsin the range of 0 to C. A typical example of such a resin is thereaction product of dilinoleic acid and ethylene diamine. Thepreparation of these resins is described in greater detail in Cowman etal., US. Patent 2,450,940, Renfrew et al., US. Patent 2,705,223, Peermanet al., US. Patent 2,881,194 and Peerman et al., US. Patent 2,886,543,inter alia.

The etherified amine-aldehyde resins are alcoholsoluble, thermosettingresins prepared by condensation of an excess of a lower aliphaticaldehyde, such as e.g. formaldehyde or acetaldehyde, with urea ormelamine and etherification of the resulting product with a 3 to 8carbon alkanol such as propanol, butanol, 'isobutanol, n-hexanol or thelike. The etherification is effected by carrying out the condensation inthe presence of the alkanol or by adding the 'alkanol after condensationhas taken place. This is normally accomplished in an acid environment.Many such resins are available commercially. More details of thepreparation and properties of these resins are disclosed'in Moore, US.Patent 2,218,474, Robinson et al., US. Patent 2,346,083, Myers, US.Patent 2,367,423 and Encyclopedia of Chemical Technology 1, 758 (1947).

The maleic-modified propylene polymers employed in the present inventionare solid, resinous polymeric materials containing about 0.05 to about5%, and preferably about 0.25 to about 4%, chemically combined maleicanhydride by weight of the polymer. Such modified polymers can beprepared by reacting maleic anhydride with 3 4 any solid propylenepolymer, either amorphous or crysdispersion was applied to the metal.The primer coats talline, containing active centers or sites which arecapable were applied to the substrates by brushing and were air ofanchoring the maleic anhydride thereon. Active centers dried for about30 minutes prior to the application of at which anchoring will occur canreadily be induced the topcoat.

on the propylene polymers in known ways, as for ex- Each prime coatingwas then topcoated with a 3 mil ample, by subjecting the polymer to theaction of high coating of crystalline polypropylene, stabilized with0.5%

energyionizing radiations or by contacting the polymer,crotonaldehyde-butylated cresol reaction product and either as a solidor a solution in a solvent, with a free 0.25% dilaurylthiodipropionate.The topcoat was applied radical-producing material such as dibenzoylperoxide, in two coats by spraying a dispersion of 100 parts ofcrysdilauroyl peroxide, dicnmyl peroxide, t-butyl perbenzoate, 1Otalline polypropylene particles having an average diameter and the like.Preferably, the modified propylene polyof 30-50 mils in 300 partsXylene, air drying for to mers are prepared by reacting maleic anhydridewith a minutes, baking for 5 minutes at 400 F., recoating, bakingsolution of the polymer in an organic solvent containing 7 minutes at400 F., and then quenching in water at a free radical-producingmaterial, such method being deroom temperature. scribed in BelgianPatent 607,269. The propylene poly- 15 Corrosion creepage resistance wasevaluated on the mer which serves as a starting material for thepreparacoated panels and simultaneously on several control pan tion ofthese modified polymers can either be an amorels coated with maleicanhydride-modified polypropylene phous polymer, otherwise known asatactic polypropylene, without the cross-linking agent of this proposal.These or a crystalline polymer of syndiotactic or isotacticstrucevaluations were performed by cutting a score mark ture. Amorphouspolypropylene is generally preferred as 20 through both the topcoat andthe primer and exposing the the starting material because its maleicanhydride modianel to a salt fog environment for 500 hours at atemfication is soluble at ordinary temperatures in a variety perature ofabout 95 F. The salt fog environment was of common organic solvents andthus the application of created by atomizing 5% aqueous NaCl. Afterexposure, the modified polymer by ordinary solution techniques is thecoatings were peeled back perpendicularly from the possible. Maleicanhydride-modified crystalline polyproscore mark as far as possible.Results reported are the pylene is not soluble in common solvents exceptat reladistance that the coatings could be peeled readily.

TABLE Example Primer Type Percent MA Cross-linking Additive AdditiveCon- Primer Thick- Salt-Fog Test N0- centration, perness, (mils)Corrosion Creep 1 cent ('0 (inches) 2 Amorphous 1. 5 %3 3..Crystalline 1. 4 3 4 2 4 do.-. 1.4 a 5 morpho 1. 5 1 0. 2-0. 5 -Vsw(10.. 1. 5 5 0. 2-0. 5 /l6 6 do 1. 5 10 0. 20. 5 /us Crystalline... 1.45 0 2 V Amorphous 1.5 1 (1.2-0.5 d0 1.5 5 (1.2-0.5 /q 10 .do 1. 5 10 0.20. 5 lies Crystalline. 1.4 5 0.2 /q 12 Amorphous 1. 5 1 0. 2-0. 5 /s%13. rystalline. 1. 4 5 0, 2 Va 14. do 1.4 1 0.2 34 15. .d0 1.4 5 0.2 16.moo 1.4 10 0.2 Vq 17 Armorphous 1.4 5 03 1 Reaction product. of -2 molescpichlorophydrin with -1 mole of 2,2-bis(p-hydroxyphcnvl) propane. 2Reaction product of 1 mole of melamine and 3 moles formaldehydeetherified with -2 niolcs n-butanol.

3 Reaction product of polymerized soybean oil acids and tricthylcnotetraminc.

4 Based on modified polypropylene. f y high t per tures, and thereforeis generally 1 The improved resistance of the cross-linked primer coat-P as dlsllefslon fOnOWlng Whlch the Qoatlng 1S baked ings to corrosioncreepage is readily seen from the data in to effect fusion. It can,however, be applied from a hot h bl solution if desired.

In accordance with the preferred embodiments of the invention, thecross-linking agent is added to the maleic anhydnde'modlfiad propylenepolymer an ammint must be understood, however, that the benefits of thisintween about and about 25 based on the welght of vention are notlimited to this substrate The henomenon the propylene polymer. Generallyspeaking, the additive of 0 0 bl l b is added to the modified propylenepolymer in an amount c rr creepage a pro em W1 0 er Su The examples showonly the improved corrosion creepage resistance of the maleicanhydride-modified polypropylene coatings applied to iron phosphatetreated steel. It

such that the concentration of the cross-linking func- Strata P as f tcopper The tional group is at least equal to that of the acid orcompositions of this lnvention exh1b1t1mproved resistance hydride f ti lgroup to corrosion creepage no matter what metal is employed The datapresented in the following table illustrate the as a Substrateimprovedresistance to corrosion creepage of a prime 0 As previously stated, theoccurrence of corrosion creepcoating, applied to panels of ironphosphate treated steel, age is particularly a problem with relativelythick primer which results from the addition of the cross-linking agentscoatings, on the order of 0.1 to 1 mil. Thus the addition of the instantinvention to both amorphous and crystalline f h qi ki agent to h l ianhydride modi maleic anhydride-modified polypropylene. When the polymerwas modified amorphous polypropylene, the polymer and the resinouscross-linking agent were dissolved in a common solvent and the coatingwas applied to the metal from this solution. In the case of the epoxyresin and the epoxidized polybutadiene, the solvent was toluene-methylisobutyl ketone mixture; with the polyamide resin, toluene fiedpolypropylene is particularly helpful when it is desired to apply such athick coating. However, improved coatings are achieved at any thicknessfrom about .01 to 1 mil.

What I claim and desire to protect by Letters Patent is: 1. Acomposition comprising maleic anhydride-moditied polypropylenecontaining about 0.25 to about 5%,

was used and with the etherified amine-aldehyde resin, based on theWeight of Polypropylem of chfimicany toluene i t or butane} was usgi wthe polymer bined maleic anhydride and about 0.5 to about 25% based wasmaleic anhydride-modified crystalline polypropylene, on the Weight ofmaleic anhYdTid-mdifid P yp p the modified polymer was dispersed in asolution of the of a cross-linking agent therefor selected from theclass cross-linking agent in solvent as specified above and thisconsisting of polyamide resins having the general. formu a where R and Rare aliphatic radicals and n is 0 to 10, and etherified amine-aldehyderesins, selected from the class consisting of urea-aldehyde andmelamine-aldehyde resins.

2. A composition comprising maleic anhydride-modified polypropylenecontaining about 0.25 to about 5%, based on the weight of polypropyleneof chemically combined maleic anhydride and about 0.5 to about 25% basedon the weight of maleic anhydride-modified polypropylene of a polyamideresin prepared by the reaction of polymerized soybean oil acids andtriethylene tetramine.

3. The composition of claim 2 where the maleic anhydride-modifiedpolypropylene is amorphous polypropylene.

4. The composition of claim 2 where the maleic anhydride-modifiedpolypropylene is crystalline polypropylene.

5. A composition comprising maleic anhydride-modified polypropylenecontaining 0.25 to 5%, based on the weight of polypropylene ofchemically combined maleic anhydride and 0.5 to about 25% based on theweight of maleic anhydride-modified polypropylene of an etherifiedamine-formaldehyde resin prepared by etherifying the reaction product ofabout 1 mole of melamine, and about 3 moles of formaldehyde with about 2moles of n-butanol.

6. The composition of claim 5 where the maleic anhydride-modifiedpolypropylene is amorphous polypropylene.

7. The composition of claim 5 where the maleic anhydride-modifiedpolypropylene is crystalline polypropylene.

References Cited UNITED STATES PATENTS 3,250,823 5/1966 Zeitlin 260-857FOREIGN PATENTS 607,269 8/ 1960 Belgium. 693,098 8/1964 Canada.

MURRAY TILLMAN, Primary Examiner.

SAMUEL H. BLECH, Examiner.

P. LIEBERMAN, Assistant Examiner.

